There are various references directed to the concept of increasing the performance of ammunition such as bullets and shotgun shells. The contents of each of the references discussed herein are incorporated by reference for all purposes.
Fibranz, U.S. Pat. No. 4,593,622, describes an industrial cartridge having two propellant sections. A flash tube has a thinner end wall than side wall. As a result of this configuration, the flame passes through the end of the flash tube to ignite the first propellant section. The second propellant charge is adjacent to the first propellant section such that ignition of the first propellant section results in ignition of the second propellant section.
Crilly, U.S. Pat. No. 5,880,397, is directed to ammunition having two propellant regions. A first propellant region contains low velocity propellant and is located between the primer and the projectile. A second propellant region contains high velocity propellant and is located around an outer surface of the primer.
Dindl, U.S. Pat. No. 7,207,276, discloses non-lethal ammunition having a two-stage firing. The ammunition includes an inner propellant region and an outer propellant region that extends around the inner propellant region. The outer and inner propellant regions are ignited using separate primers.
Schluckebier et al., U.S. Pat. No. 8,220,393, is directed to ammunition having two propellant regions. A first propellant region is located along a central axis of the ammunition between the primer and the payload. The second propellant region is located radially outward from the first propellant region such that the second propellant region is between the first propellant region and a casing of the ammunition.
Thouin, French Patent No. 78,417, describes ammunition having a first propellant region that is located along a central axis of the ammunition between the primer and the payload. Similar to Schluckebier, which is discussed above, a second propellant region is located radially outward from the first propellant region such that the second propellant region is between the first propellant region and a casing of the ammunition.
Chetcuti, Canadian Patent Publication No. 2,173,968, discloses ammunition that is configured to reduce recoil typically associated with shotgun ammunition. The ammunition includes a plurality of toric members mounted to an outer surface of the flash tube. Each of the toric members has an air space therein, which enables the toric members to deflect and thereby absorb the recoil.